Corrugated pattern forming sheet, and methods for manufacturing antireflector, retardation plate, original process sheet plate, and optical element

ABSTRACT

A corrugated pattern forming sheet exhibiting excellent performance when being used as optical elements, such as an antireflector and a retardation plate is provided. A corrugated pattern forming sheet of the invention includes a resin layer, and a hard layer provided at least in a portion of an outer surface of the resin layer. The hard layer is made of a metal or a metallic compound. The hard layer has a wavelike corrugated pattern. The average pitch of the corrugated pattern is 1 μm or less, and the average depth of the bottom of the corrugated pattern is 10% or more given an average pitch of 100%.

RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.11/746,018, filed May 8, 2007, which claims priority to Japanese PatentApplication No. 2006-131281, filed May 10, 2006; Japanese PatentApplication No. 2007-040693, filed Feb. 21, 2007; and Japanese PatentApplication No. 2007-104714, filed Apr. 12, 2007, the entire contents ofwhich are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a corrugated pattern forming sheetprovided in optical elements, such as an antireflector and a retardationplate, and a method for manufacturing the same. The present inventionalso relates to an antireflector and a retardation plate in which thecorrugated pattern forming sheet is used. The present invention alsorelates to an original process sheet plate, which is used as a die formanufacturing a sheet having a corrugated pattern. Moreover, the presentinvention relates to a method for manufacturing an optical element.

BACKGROUND OF THE INVENTION

It is known (refer to “Optics” (Volume 27, No. 1, 1998, Pages 12-17)written by Hisao Kikuta and Koichi Iwata and issued by the OpticalSociety of Japan) that a corrugated pattern forming sheet in which acorrugated pattern composed of minute wavelike irregularities is formedon a surface and the average pitch of the corrugated pattern is belowthe wavelength of visible light can be utilized as optical elements,such as an antireflector and a retardation plate.

Here, the average pitch is an average value of the pitch that is thedistance between an apex of a convex portion of the corrugated patternand an apex of a convex portion adjacent to the convex portion in a casewhere the corrugated pattern runs only in one direction. On the otherhand, the average pitch is obtained as follows in a case where thecorrugated pattern does not run in a specific direction. First, the topsurface of a corrugated pattern is captured by an atomic forcemicroscope, and the image is converted into a gray-scale file (forexample, tiff format, etc.).

In an image (refer to FIG. 4) of the gray-scale file, a lower whitenessmeans that a bottom of a concave portion is deeper (a higher whitenessmeans that an apex of a convex portion is higher). Next, the image ofthe gray-scale file is Fourier-transformed. The image after the Fouriertransformation is shown in FIG. 5. In the image after the Fouriertransformation, the direction as seen from the center of a white portionrepresents the directivity of the gray-scales, and the inverse number ofthe distance from the center to the white portion represents the periodof the gray-scale image. In a case where the corrugated pattern does notrun in a specific direction, an image showing a white circular ring likeFIG. 6 is obtained. Next, the luminance (Y-axis) with respect to thedistance (X-axis) from the center of the circular ring is plotted bydrawing a linear auxiliary line L2 from the center of the circular ringin the image after the Fourier transformation towards the outside (referto FIG. 4). Then, a value r on the X-axis showing a maximal value in theplot is read. The inverse number (1/r) of this value r is an averagepitch.

The corrugated pattern forming sheet can be utilized as an antireflectoron the basis of the following reasons.

In a case where the corrugated pattern is not provided in a sheetsurface, reflection is caused by an abrupt change in refractive index inan interface between the sheet and air. However, in a case where awavelike corrugated pattern is provided in a sheet surface, i.e., aninterface between the sheet and air, a value (hereinafter referred to as“middle refractive index”) between the refractive index of air and therefractive index of a corrugated pattern forming sheet is shown in aportion of the corrugated pattern, and moreover, the middle refractiveindex continuously changes in the depth direction of the corrugatedpattern. Specifically, the refractive index of a deeper positionapproaches the refractive index of the corrugated pattern forming sheet.Because the middle refractive index continuously changes in this way,reflection of light can be suppressed without causing an abrupt changein refractive index in the interface as described above. Further, if thepitch of a corrugated pattern is below the wavelength of visible light,coloring by diffraction of visible light, i.e., interference of visiblelight, in a portion of the corrugated pattern is hardly caused.

Further, the corrugated pattern forming sheet can be utilized as aretardation plate because a portion of the corrugated pattern showsoptical anisotropy against the light that is incident on the corrugatedpattern with the result that air and a corrugated pattern forming sheetwhose refractive indexes are different from each other are arrangedalternately. Moreover, if the pitch of a corrugated pattern becomesapproximately equal to or less than the wavelength of visible light, aphenomenon in that the same retardation is shown in a broad visiblelight wavelength range will appear.

As a specific example of such a corrugated pattern forming sheet, forexample, a sheet in which gold is vapor-deposited on one surface of asheet made of heated polydimethyl siloxane to form a metal layer, andthen cooled, whereby the sheet made of polydimethyl siloxane is made toshrink, thereby forming a wavelike corrugated pattern in the surface ofthe metal layer, is suggested in “Nature” (No. 393, 1998, Page 146)written by Ned Bowden.

Further, a sheet in which a foundation layer and a metal layer aresequentially formed in the surface of a heat-shrinkable synthetic resinfilm, and then the heat-shrinkable synthetic resin film is made tothermally shrink to form a wavelike corrugated pattern in the surface ofthe metal layer is suggested in JP-A-Sho63-301988.

A sheet in which a layer made of a material that is reduced in volume byexposure is formed, and the layer is exposed to form irregularities in asurface thereof is suggested in JP-A-2003-187503.

However, none of the corrugated pattern forming sheets described inJP-A-Sho63-301988, JP-A-2003-187503, and “Nature” written by Ned Bowdenshow excellent performance as optical elements. Specifically, when thecorrugated pattern forming sheets are used as antireflectors, thereflectance cannot be made low enough, and when the corrugated patternforming sheets are used as retardation plates, the retardation cannot bemade large enough, and the same retardation cannot be caused over abroad wavelength range.

Further, photolithography by the visible light that uses a pattern maskis known as a method for manufacturing a corrugated pattern formingsheet. However, a corrugated pattern forming sheet with a pitch belowthe wavelength of the light that can be utilized as an optical elementcannot be manufactured by this method. Therefore, it is necessary toapply an ultraviolet laser interference method or electron beamlithography that allows finer processing. In these methods, a resistlayer formed on a substrate is exposed and developed with ultravioletlaser interference light or electron beams to form a resist patternlayer, and irregularities are formed by a dry etching method, etc. byusing the resist pattern layer as a mask. However, when the ultravioletlaser interferometer method or electron beam lithography is applied,there is a problem in that this method is not suitable for massproduction because processing in a broad region which exceeds 10 cm isdifficult.

A method for arranging a particle layer on a substrate and dry-etchingthe surface of the substrate by using the particle layer as an etchingmask is also suggested in JP-A-2005-279807. However, there is a problemin that this method is also not suitable for mass production becauseprocessing in a broad region which exceeds 30 cm is difficult.

SUMMARY OF THE INVENTION

The invention has been made in view of the above situations. Therefore,an object of the invention is to provide a corrugated pattern formingsheet exhibiting excellent performance when being used as opticalelements, such as an antireflector and a retardation plate. Anotherobject of the invention is to provide a method for manufacturing acorrugated pattern forming sheet capable of simply and easilymanufacturing such a corrugated pattern forming sheet with large area.Still another object of the invention is to provide an antireflectorwith a low reflectance, and a retardation plate which causes the sameretardation over a broad wavelength range. A still further object of theinvention is to provide an original process sheet plate capable ofsimply and easily manufacturing a suitable sheet forming a corrugatedpattern as an optical element on a large scale. A still further objectof the invention is to provide a method for manufacturing an opticalelement capable of simply and easily manufacturing an optical elementhaving a corrugated pattern of a suitable average pitch and averagedepth for an optical element on a large scale.

The present inventors have invented the following corrugated patternforming sheet, as a result of studying improvements in the performanceof optical elements, such as an antireflector and a retardation plate.The present inventors have also invented the following method formanufacturing a corrugated pattern by studying a method formanufacturing such a corrugated pattern forming sheet. Also, the presentinventors have invented a method for manufacturing the followingantireflector, retardation plate, original process sheet plate, andoptical element.

(1) A corrugated pattern forming sheet comprising a resin layer, and ahard layer provided at least in a portion of an outer surface of theresin layer, the hard layer having a wavelike corrugated pattern,wherein the hard layer is made of a metal or a metallic compound, andthe average pitch of the corrugated pattern is 1 μm or less, and theaverage depth of the bottom of the corrugated pattern is 10% or moregiven an average pitch of 100%.(2) The corrugated pattern forming sheet according to (1), wherein thehard layer is made of a metallic compound.(3) The corrugated pattern forming sheet according to (2), wherein themetallic compound is at least one kind of metallic compound selectedfrom the group consisting of titanium oxide, aluminum oxide, zinc oxide,magnesium oxide, tin oxide, copper oxide, indium oxide, cadmium oxide,lead oxide, silicon oxide, barium fluoride, calcium fluoride, magnesiumfluoride, zinc sulfide, and gallium arsenide.(4) The corrugated pattern forming sheet according to (1), wherein thehard layer is made of a metal.(5) The corrugated pattern forming sheet according to (4), wherein themetal is at least one kind of metal selected from the group consistingof gold, aluminum, silver, carbon, copper, germanium, indium, magnesium,niobium, palladium, lead, platinum, silicon, tin, titanium, vanadium,zinc, and bismuth.(6) A method for manufacturing a corrugated pattern forming sheetcomprising: providing a hard layer having a smooth surface at least in aportion of an outer surface of a resin layer to form a laminated sheet;and meanderingly deforming at least the hard layer of the laminatedsheet, wherein the hard layer is made of a metal or a metallic compound.(7) An antireflector comprising the corrugated pattern forming sheet ofany one of (1) to (5).(8) A retardation plate comprising the corrugated pattern forming sheetof any one of (1) to (5).(9) An original process sheet plate, comprising the corrugated patternforming sheet of any one of (1) to (5), and used as a die formanufacturing a sheet having a corrugated pattern with a same averagepitch and average depth as the corrugated pattern forming sheet.(10) A method for manufacturing an optical element comprising: a step inwhich an uncured curable resin is coated on a surface of the originalprocess sheet plate of (9), in which the corrugated pattern is formed;and a step in which a cured coating film is peeled from the originalprocess sheet plate after curing the curable resin.(11) A method for manufacturing an optical element comprising: a step inwhich a sheet-like thermoplastic resin is contacted with a surface ofthe original process sheet plate of (9), in which the corrugated patternis formed; a step in which the thermoplastic resin is cooled aftersoftening by heating while pressing to the original process sheet plate;and a step in which the cooled sheet-like thermoplastic resin is peeledfrom the original process sheet plate.(12) A method for manufacturing an optical element comprising: a step inwhich a material for transferring a corrugated pattern is laminated on asurface of the original process sheet plate of (9), in which thecorrugated pattern is formed; a step in which a secondary process sheetis prepared by peeling the material for transferring the corrugatedpattern laminated on the corrugated pattern from the original processsheet plate; a step in which an uncured curable resin is coated on asurface of the secondary process sheet which has contacted to thecorrugated pattern of the original process sheet plate; and a step inwhich a cured coating film is peeled from the secondary process sheetafter curing the curable resin.(13) A method for manufacturing an optical element comprising: a step inwhich a material for transferring a corrugated pattern is laminated on asurface of the original process sheet plate of (9), in which thecorrugated pattern is formed; a step in which a secondary process sheetis prepared by peeling the material for transferring the corrugatedpattern laminated on the corrugated pattern from the original processsheet plate; a step in which a sheet-like thermoplastic resin iscontacted with a surface of the secondary process sheet which hascontacted to the corrugated pattern of the original process sheet plate;a step in which the thermoplastic resin is cooled after softening byheating while pressing to the secondary process sheet; and a step inwhich the cooled sheet-like thermoplastic resin is peeled from thesecondary process sheet.

The corrugated pattern forming sheet of the invention can be suitablyutilized as optical elements, such as an antireflector and a retardationplate. The corrugated pattern forming sheet of the invention can also besuitably utilized as an original process sheet plate to be used as a diefor manufacturing an optical element having a wavelike corrugatedpattern.

Since a fine corrugated pattern can be easily formed in a surface with alarge area by the method for manufacturing a corrugated pattern formingsheet of the invention, the corrugated pattern forming sheet which canbe suitably utilized for optical elements, etc. can be easily and simplymanufactured with large area on a large scale.

The antireflector of the invention has a low reflectance, and hasexcellent performance.

The retardation plate of the invention can cause the same retardationover a broad wavelength range, and has excellent performance.

By using the original process sheet plate of the present invention, asheet forming a corrugated pattern of a suitable average pitch andaverage depth for an optical element can be simply and easilymanufactured on a large scale.

According to a method for manufacturing an optical element of thepresent invention, an optical element having a corrugated pattern of asuitable average pitch and average depth for an optical element can besimply and easily manufactured on a large scale.

BRIEF DESCRIPTION OF THE DRAWINGS

Some of the features and advantages of the invention have beendescribed, and others will become apparent from the detailed descriptionwhich follows and from the accompanying drawings, in which:

FIG. 1 is an enlarged perspective view showing an enlarged portion ofone embodiment of a corrugated pattern forming sheet of the invention.

FIG. 2 is a sectional view of the corrugated pattern forming sheet ofFIG. 1 when being cut in a direction orthogonal to a direction in whicha corrugated pattern is formed.

FIG. 3 is a sectional view showing a laminated sheet in one embodimentof a method for manufacturing the corrugated pattern forming sheet ofthe invention.

FIG. 4 shows a gray-scale conversion image of the image obtained bycapturing the surface of a corrugated pattern which does not run in aspecific direction by an atomic force microscope.

FIG. 5 shows an image obtained by Fourier-transforming the image of FIG.4.

FIG. 6 is a graph obtained by plotting the luminance to the distancefrom the center of a circular ring in the image of FIG. 5.

FIG. 7 is a view illustrating an example of a method for manufacturingan optical element, using the corrugated pattern forming sheet of theinvention.

DETAILED DESCRIPTION OF THE INVENTION

The invention summarized above and defined by the enumerated claims maybe better understood by referring to the following detailed description,which should be read with reference to the accompanying drawings. Thisdetailed description of particular preferred embodiments, set out belowto enable one to build and use particular implementations of theinvention, is not intended to limit the enumerated claims, but to serveas particular examples thereof.

(Corrugated Pattern Forming Sheet)

One embodiment of a corrugated pattern forming sheet of the inventionwill be described.

A corrugated pattern forming sheet of the present embodiment is shown inFIG. 1. The corrugated pattern forming sheet 10 of the presentembodiment includes a resin layer 11, and a hard layer 12 provided inone whole surface of the resin layer 11, and the hard layer 12 has aperiodic wavelike corrugated pattern 12 a along the width direction ofthe corrugated pattern forming sheet 10.

The resin layer 11 is made of, for example, polyesters, such aspolyethylene terephthalate; polyolefins, such as polyethylene andpolypropylene; polystyrene-based resins, such as styrene butadiene blockcopolymers; silicone resins, such as polydimethyl siloxane; and resins,such as polyvinyl chloride, polyvinylidene chloride, fluororesin, ABSresin, polyamide, acrylic resin, polycarbonate, and polycycloolefin.

The thickness of the resin layer 11 is preferably 0.3 to 500 μm. If thethickness of the resin layer 11 is 0.3 m or more, the corrugated patternforming sheet 10 is hardly broken, and if the thickness of the resinlayer is 500 μm or less, the corrugated pattern forming sheet 10 can bemade thin easily. Further, in order to support the resin layer 11, abase member made of resin having a thickness 5 to 500 μm may beprovided.

The hard layer 12 is made of a metal or metallic compound.

As the metal, at least one kind of metal selected from the groupconsisting of gold, aluminum, silver, carbon, copper, germanium, indium,magnesium, niobium, palladium, lead, platinum, silicon, tin, titanium,vanadium, zinc, and bismuth is preferable because a Young's modulus doesnot become too high and the corrugated pattern 12 a is formed moreeasily. The term “metal” also includes semi-metals of carbon, germanium,tin, etc.

As the metallic compound, at least one kind of metallic compoundselected from the group consisting of titanium oxide, aluminum oxide,zinc oxide, magnesium oxide, tin oxide, copper oxide, indium oxide,cadmium oxide, lead oxide, silicon oxide, barium fluoride, calciumfluoride, magnesium fluoride, zinc sulfide, and gallium arsenide ispreferable for similar reasons. Among them, titanium oxide is preferablebecause it is a photocatalyst which decomposes an organic matteradhering to a surface when it is irradiated with light, and has aself-cleaning function.

In addition, in a case where the hard layer 12 is made of metal, thesurface of the layer may be air-oxidized, thereby forming an airoxidization film. However, in the invention, the surface of such a metallayer which is air-oxidized is also considered as a layer made of metal.

The thickness of the hard layer 12 is preferably 1 to 30 nm. If thethickness of the hard layer 12 is 1 nm or more, defects are hardlydeveloped in the hard layer 12, and if the thickness is 30 nm or less,the hard layer 12 can secure optical transparency sufficiently.

Further, the thickness of the hard layer 12 is more preferably 10 nm orless, and particularly preferably 5 nm or less. If the thickness of thehard layer 12 is 10 nm or less, a corrugated pattern forming sheet canbe easily manufactured as described later.

Further a primer layer may be formed between the resin layer 11 and thehard layer 12 for the purpose of an improvement in adhesiveness, andformation of a finer structure.

Moreover, a resin layer may be provided on the hard layer 12. Theaverage pitch A of the corrugated pattern 12 a of the corrugated patternforming sheet 10 is 1 μm or less, preferably 0.7 μm or less, and morepreferably 0.4 μm or less. Further, the average pitch A is preferably0.05 μm or more in that the corrugated pattern 12 a can be easilyformed.

Here, the average pitch A is an average value of individual pitch A₁,A₂, A₃, . . . .

Further, in a case where a corrugated pattern spreads not in onedirection but in two dimensions, the average pitch is obtained by amethod for Fourier-transforming an image of the corrugated pattern.Specifically, the average pitch is obtained as follows.

First, an image of a top surface of a corrugated pattern captured by anatomic force microscope is converted into a gray-scale file, and theimage (refer to FIG. 4) of the file is Fourier-transformed, therebyobtaining a white annular image (refer to FIG. 5). Next, the luminance(Y-axis) with respect to the distance (X-axis) from the center of thecircular ring seen in the image after the Fourier transformation isplotted (refer to FIG. 6).

Then, a value r on the X-axis showing a maximal value in the plot isread, and an inverse number (1/r) of this r is adopted as the averagepitch.

The average depth B of the bottom 12 b of the corrugated pattern 12 a is10% or more, preferably 30% or more, and more preferably 100% or more,when the average pitch A is 100%. Further, the average depth B ispreferably 500% or less when the average pitch A is 100% in that thecorrugated pattern 12 a can be easily formed.

Here, the bottom 12 b is an inflection point of a concave portion of thecorrugated pattern 12 a. The average depth B is a difference(b_(AV)−B_(AV)) between an average value (B_(AV)) of lengths B₁, B₂, B₃,. . . from a reference line L1 parallel to the direction of a surface ofthe whole corrugated pattern forming sheet 10 to the apex of each convexportion and an average value (b_(AV)) of lengths b₁, b₂, b₃, . . . fromthe reference line L1 to the bottom of each concave portion, when across section (refer to FIG. 2) obtained by cutting the corrugatedpattern forming sheet 10 along its longitudinal direction is seen.

The apex of the convex portion and the bottom of the concave portiontouch the surface of the hard layer 12 opposite to the resin layer 11.

It was proven as a result of the present inventor's investigation thatthe corrugated pattern forming sheet exhibits excellent performance asan optical element if the average pitch A of the corrugated pattern 12 ais 1 μm or less, and particularly 0.4 μm or less, and the average depthB of the bottom 12 b of the corrugated pattern 12 a is 10% or more, andparticularly 100% or more when the average pitch A is 100%.Specifically, it was proven that the reflectance can be lowered when thecorrugated pattern forming sheet 10 is used as the antireflector, andthe same retardation can be caused over a broad wavelength range whenthe corrugated pattern forming sheet is used as a retardation plate.

This is caused by the fact that the average pitch A of the corrugatedpattern 12 a is as short as 1 μm, and the average depth B is as large as10% when the average pitch A is 100%. That is, the average pitch A isshort, and becomes equal to or less than the wavelength of visiblelight. As a result, diffraction or diffusion of the visible light due tocorrugatedness is hardly caused. In addition, since the average depth Bis large, a portion where a middle refractive index changes continuouslybecomes long in the thickness direction. Therefore, the effect ofsuppressing reflection of light can be exhibited markedly. Further,since the average pitch A is short and the average depth B is large, aportion where air and the corrugated pattern forming sheet whoserefractive indexes are different from each other are alternatelyarranged becomes long in the thickness direction. As a result, since aportion showing optical anisotropy becomes long, a retardation can becaused. Moreover, retardations caused by such a corrugated pattern 12 abecome approximately equal to each other over a broad wavelength range.

All the pitches A₁, A₂, A₃, . . . of the corrugated pattern 12 a arepreferably within a range of ±60% of the average pitch A, and morepreferably within a range of ±30% of the average pitch A. If each of thepitches is within a range of ±60% of the average pitch A, the pitchesbecome uniform. As a result, the corrugated pattern forming sheetexhibits further excellent performance as an optical element.

Further, the pitches may change continuously such that each of thepitches A₁, A₂, A₃, satisfies that the average pitch A is 1 μm or less.

All the depths B₁, B₂, B₃, . . . of the corrugated pattern 12 a arepreferably within a range of ±60% of the average depth B, and morepreferably within a range of ±30% of the average depth B. If each of thedepths is within a range of ±60% of the average depth B, the depthsbecome uniform. As a result, the corrugated pattern forming sheetexhibits further excellent performance as an optical element.

Further, the depths may change continuously such that each of the depthsB₁, B₂, B₃, . . . satisfies that the average depth B is 10% or more whenthe average pitch A is 100%.

As well as the corrugated pattern forming sheet 10 of the invention, asdescribed later, being applied to optical elements, such as anantireflector and a retardation plate, and a process sheet formanufacturing an optical element, it can also be utilized as asuperhydrophobic or superhydrophillic sheet.

In addition, the corrugated pattern forming sheet of the invention isnot limited to the above-described embodiment. For example, in theabove-described embodiment, the hard layer has a wavelike corrugatedpattern which is periodic along the width direction of a corrugatedpattern forming sheet. However, the hard layer may have a wavelikecorrugated pattern which is periodic along the longitudinal direction ofa corrugated pattern forming sheet other than the corrugated pattern.Furthermore, a hard layer may have a number of wavelike corrugatedpatterns which do not run in a specific direction. Even in this case,the corrugated pattern forming sheet exhibits excellent performance asan optical element if the average pitch of a corrugated pattern is 1 μmor less, and the average depth of the bottom of the corrugated patternis 10% or more given an average pitch of 100%.

Although the convex portion preferably has a sharpened tip in terms ofrefractive index, the convex portion may have a rounded tip. In a casewhere a hard layer has a wavelike corrugated pattern which does not runin a specific direction, as a method for measuring the average depth, amethod for measuring the depth of each bottom using a cross-sectionalimage of a corrugated pattern captured by an atomic force microscope andcalculating the average value of the depths of the bottoms is adopted.

(Method for Manufacturing Corrugated Pattern Forming Sheet)

One embodiment of a method for manufacturing the corrugated patternforming sheet of the invention will be described.

The method for manufacturing a corrugated pattern forming sheet of theembodiment, as shown in FIG. 3, is a method having a process forproviding a hard layer 13 having a smooth surface (hereinafter referredto as “smooth surface hard layer 13”) in one whole surface of a resinlayer 11 to form a laminated sheet 10 a and a process of meanderinglydeforming at least the smooth surface hard layer 13 of the laminatedsheet 10 a. Here, the smooth surface hard layer 13 is a layer having acenterline average roughness of 0.1 μm or less described in JIS B0601.

In this method, the smooth surface hard layer 13 is made of a metal ormetallic compound. By making the smooth surface hard layer 13 of a metalor metallic compound, the smooth surface hard layer 13 is bent like awave and meanderingly deformed while the resin layer 11 is deformed atthe time of compression, and thus the corrugated pattern 12 a can beformed easily.

As this manufacturing method, for example, the following methods (1) to(5) can be used.

(1) A method for providing a smooth surface hard layer 13 in one wholesurface of a resin layer 11 to form a laminated sheet 10 a, andcompressing the whole laminated sheet 10 a in one direction along thesurface thereof.

(2) A method for providing a smooth surface hard layer 13 in one wholesurface of a resin layer 11 made of a shrink film that thermally shrinksuniaxially or biaxially to form a laminated sheet 10 a, and making theresin layer 11 thermally shrink to compress the smooth surface hardlayer 13 laminated on the resin layer 11 in one direction or two or moredirections along the surface thereof.

(3) A method for providing a smooth surface hard layer 13 in one wholesurface of a resin layer 11 to form a laminated sheet 10 a, stretchingthe laminated sheet 10 a in one direction, and making the laminatedsheet 10 a shrink in a direction orthogonal to the stretching directionto compress the smooth surface hard layer 13 in one direction along thesurface thereof.

(4) A method for laminating a smooth surface hard layer 13 on a resinlayer 11 formed from an uncured ionizing radiation-curable resin to forma laminated sheet 10 a, and irradiating the resin layer 11 with ionizingradiation to cure and shrink the resin layer, thereby compressing thesmooth surface hard layer 13 laminated on the resin layer 11 in onedirection along the surface thereof.

(5) A method for laminating a smooth surface hard layer 13 on a resinlayer 11 that is swelled and expanded with a solvent to form a laminatedsheet 10 a, and drying and removing the solvent in the resin layer 11 toshrink the resin layer 11, thereby compressing the smooth surface hardlayer 13 laminated on the resin layer 11 in one direction along thesurface thereof.

The method for laminating a laminated sheet 10 a in the method (1) mayinclude, for example, a method for vapor-depositing a metal or metalliccompound on one surface of a resin layer 11, a method for laminating apreviously prepared smooth surface hard layer 13 on one surface of aresin layer 11, etc.

Since the corrugated pattern 12 a can be more easily formed by thismanufacturing method, the Young's modulus of the smooth surface hardlayer 13 is preferably set to 0.1 to 500 GPa, and more preferably set to1 to 150 GPa.

In order to make the Young's modulus of the smooth surface hard layer 13fall within the above the range, the smooth surface hard layer 13 ispreferably made of at least one kind of metal selected from the groupconsisting of gold, aluminum, silver, carbon, copper, germanium, indium,magnesium, niobium, palladium, lead, platinum, silicon, tin, titanium,vanadium, zinc, and bismuth. Otherwise, the smooth surface hard layer 13is preferably made of at least one kind of metallic compound selectedfrom the group consisting of titanium oxide, aluminum oxide, zinc oxide,magnesium oxide, tin oxide, copper oxide, indium oxide, cadmium oxide,lead oxide, silicon oxide, barium fluoride, calcium fluoride, magnesiumfluoride, zinc sulfide, and gallium arsenide.

Here, the Young's modulus is a value measured by changing temperature to23° C. by the “Method for testing the Young's modulus of a metallicmaterial at an elevated temperature” of JIS Z 2280-1993.

This is the same even in a case where the hard layer is made of ametallic compound.

The thickness of the smooth surface hard layer 13 is preferably 10 nm orless, more preferably 7 nm or less, and especially preferably 5 nm orless. If the thickness of the smooth surface hard layer 13 is 10 nm orless, the average pitch A of the corrugated pattern 12 a can be reliablyset to 1 μm or less.

Further, since defects are hardly developed in the hard layer 12 aftercompression, the smooth surface hard layer 13 is preferably 1 nm ormore.

Further, the thickness of the smooth surface hard layer 13 may changecontinuously. In a case where the thickness of the smooth surface hardlayer 13 changes continuously, the pitches A₁, A₂, A₃, and depths B₁,B₂, B₃, . . . of the corrugated pattern 12 a formed after compressionwill change continuously.

The method for compressing the whole laminated sheet 10 a in onedirection along the surface thereof may include, for example, a methodof pulling and stretching one end and its opposite end of the laminatedsheet 10 a while fixing them with a vise, etc.

When the laminated sheet 10 a is transformed in one direction, it ispreferable to transform the smooth surface hard layer 13 at adeformation ratio of 5% or more and it is more preferable to transformthe smooth surface hard layer 13 at a deformation ratio of 30% or more.If the smooth surface hard layer 13 is transformed at a deformationratio of 5% or more, the average depth B of the bottom 12 b of thecorrugated pattern 12 a can be easily set to 10% or more when theaverage pitch A is 100%.

Furthermore, it is more preferable to transform the smooth surface hardlayer 13 at a deformation ratio of 50% or more. If the smooth surfacehard layer 13 is transformed at a deformation ratio of 50% or more, theaverage depth B of the bottom 12 b of the corrugated pattern 12 a can beeasily set to 100% or more when the average pitch A is 100%.

Here, the deformation ratio is (length after deformation−length beforedeformation)/(length before deformation)×100(%). Otherwise, thedeformation ratio is (deformed length)/(length beforedeformation)×100(%).

When the smooth surface hard layer is deformed two-dimensionally, it ispreferable to set the deformation ratio in a direction in which thesmooth surface hard layer deforms most largely to 5% or more, and it ismore preferable to set the deformation ratio to 50% or more.

As the shrink film to be used as the resin layer 11 in the method (2),for example, a polyethylene-terephthalate-based shrink film, apolystyrene-based shrink film, a polyolefin-based shrink film, apolyvinyl-chloride-based shrink film, etc. can be used. Among the shrinkfilms, a shrink film that shrinks as much as 50 to 70% is preferable. Ifthe shrink film that shrinks as much as 50 to 70% is used, the abovedeformation ratio can be set to 50% or more, and the corrugated patternforming sheet 10 in which the average pitch A of the corrugated pattern12 a is 1 μm or less, and the average depth B of the bottom 12 b of thecorrugated pattern 12 a is 10% or more when the average pitch A is 100%can be manufactured easily. Furthermore, the corrugated pattern formingsheet 10 in which the average depth B of the bottom 12 b of thecorrugated pattern 12 a is 100% or more when the average pitch A is 100%can also be manufactured easily. In addition, a stretch film may be usedinstead of a shrink film.

The heating method when the resin layer 11 is made to thermally shrinkmay include methods of passing a corrugated pattern forming sheetthrough hot air, steam, and hot water. Among these methods, the methodfor passing a corrugated pattern forming sheet through hot water ispreferable because it can make the sheet shrink uniformly.

It is preferable that the heating temperature when the resin layer 11 ismade to thermally shrink will be appropriately selected according to thekind of a shrink film to be used, a desired pitch A of the corrugatedpattern 12 a, and a desired depth B of the bottom 12 b.

In a case where the shrink film is a shrink film that thermally shrinksuniaxially, the wavelike corrugated pattern 12 a is formed along adirection orthogonal to a shrinking direction. In a case where theshrink film is a shrink film that thermally shrinks biaxially, awavelike corrugated pattern which does not run in a specific directionis formed.

As for the smooth surface hard layer 13 in the method (2), the samemetal and metallic compound as those used in the method (1) can be used,and the same thickness can be selected. Further, as the method forforming a laminated sheet 10 a, similarly to the method (1), a methodfor vapor-depositing a metal or metallic compound on one surface of aresin layer 11, and a method for laminating a previously prepared smoothsurface hard layer 13 on one surface of a resin layer 11, can beapplied.

In the method (3), the method for stretching the laminated sheet 10 a inone direction may include, for example, a method for pulling andstretching one end and its opposite end of the laminated sheet 10 a.

In the method for (4), the ionizing radiation-curable resin may includeultraviolet-curable resin, electron beam curable resin, etc.

In the method (5), a solvent is appropriately selected according to thekind of resin constituting the resin layer 11. The drying temperature ofa solvent is appropriately selected according to the kind of thesolvent.

Even in the smooth surface hard layer 13 in the methods (3) to (5), thesame component as that used in the method (1) can be used, and the samethickness can be selected. Further, as the method for forming alaminated sheet 10 a, similarly to the method (1), a method forvapor-depositing a metal or metallic compound on one surface of a resinlayer 11, and a method for laminating a previously prepared smoothsurface hard layer 13 on one surface of a resin layer 11, can beapplied.

In the methods of manufacturing a corrugated pattern forming sheetdescribed above, the smooth surface hard layer 13 made of a metal ormetallic compound is incomparably larger in Young's modulus than theresin layer 11. Therefore, when the smooth surface hard layer 13 harderthan the resin layer 11 is compressed or shrunken, the smooth surfacehard layer 13 will be folded up rather than being increased inthickness. Moreover, since the smooth surface hard layer 13 is laminatedon the resin layer 11, a stress caused by compression or shrinkage isuniformly applied as a whole. Therefore, according to the invention, thecorrugated pattern forming sheet 10 can be manufactured easily bymeanderingly deforming the sheet. Accordingly, the corrugated patternforming sheet 10 having excellent performance as an optical element canbe simply and easily manufactured with large area.

Moreover, according to this manufacturing method, the average pitch A ofthe corrugated pattern 12 a can be easily made short, and average depthB of the corrugated pattern 12 a can be easily made large. Specifically,the average pitch A of the corrugated pattern 12 a can be easily set to1 μm or less, and the average depth B of the bottom 12 b of thecorrugated pattern 12 a can be easily set to 10% or more when theaverage pitch A is 100%.

Moreover, according to this manufacturing method, the pitches A₁, A₂,A₃, . . . and depths B₁, B₂, B₃, . . . in the corrugated pattern 12 acan be easily made uniform.

As conventional methods of manufacturing a corrugated pattern formingsheet, there are known a thermal nano imprinting method for pressing acorrugated pattern of a nano imprinting die against a heated andsoftened sheet-like thermoplastic resin, and then cooling thermoplasticresin, and an photo nano imprinting method for coating a corrugatedpattern of a nano imprinting die with an uncured ionizingradiation-curable resin composition, and then irradiating the resincomposition with ionizing radiation to cure it.

In the thermal nano imprinting method, it is necessary to press a diehaving a corrugated pattern against a thermoplastic resin with uniformpressure applied to the whole die. However, in such a method, if thearea of the die becomes large, the pressure applied to the die is apt tobecome nonuniform. As a result, transfer of a corrugated pattern mightbecome nonuniform. Accordingly, this thermal nano imprinting method isnot suitable for production of a corrugated pattern forming sheet withlarge area which is used for a display of a liquid crystal television,etc.

Further, since the releasability between a die and a cured resin isinadequate in the photo nano imprinting method, transfer of a corrugatedpattern might become imperfect. Moreover, this tendency becomesremarkable as the number of times of repeated use of a die increases.

In contrast, in the method for manufacturing a corrugated patternforming sheet described above, transfer of a corrugated pattern can beomitted. Thus, the above problems in the nano imprinting method can besolved.

In addition, in the above-described embodiment, a smooth surface hardlayer is provided on one whole surface of a resin layer. However, asmooth surface hard layer may be provided in a portion of one surface ofa resin layer, smooth surface hard layers may be provided on both wholesurfaces of a resin layer, and smooth surface hard layers may beprovided in portions of both surfaces of a resin layer.

(Antireflector)

The antireflector of the invention is an antireflector including theabove-described corrugated pattern forming sheet 10.

In the antireflector of the invention, one surface or both surfaces ofthe corrugated pattern forming sheet 10 may be provided with otherlayers. For example, in order to prevent staining of the surface of thecorrugated pattern forming sheet 10 on the side where the corrugatedpattern 12 a is formed, the surface may be provided with a stain-prooflayer with a thickness of about 1 to 5 nm which contains fluororesin orsilicone resin as a chief ingredient.

Also, on the surface of the corrugated pattern forming sheet 10 on theside where the corrugated pattern 12 a is not formed, the surface may beprovided with, for example, a base material. Examples of the basematerial include a sheet made of resin such as triacetylcellulose.

The antireflector of the invention shows the middle refractive indexbetween the refractive index of air, and the refractive index of thecorrugated pattern forming sheet 10 (refractive index of the resin layer11) in a portion of the wavelike corrugated pattern 12 a of thecorrugated pattern forming sheet 10, and the middle refractive indexchanges continuously. Moreover, the average pitch A of the corrugatedpattern 12 a is 1 μm or less, and the average depth B of the bottom 12 bof the corrugated pattern 12 a is 10% or more when the average pitch Ais 100%. From these facts, the reflectance of light can be madeparticularly low, and specifically, the reflectance can be set to about0%. This is because, as described above, the average pitch A of thecorrugated pattern 12 a of the corrugated pattern forming sheet 10 is asshort as 1 μm or less, and the average depth B is as large as 10% ormore when the average pitch A is 100%, and therefore a portion where themiddle refractive index changes continuously becomes long in thethickness direction, so that the effect of suppressing reflection oflight can be exhibited markedly.

Such the antireflector is attached to, for example, an image displaydevice, such as a liquid crystal display panel or a plasma display, atip of a light-emitting part of a light-emitting diode, the surface of asolar battery panel, etc.

In a case where the antireflector is attached to the image displaydevice, reflection of illumination can be prevented. Therefore, thevisibility of an image improves. In a case where the antireflector isattached to the tip of the light-emitting part of the light-emittingdiode, the extraction efficiency of light improves. In a case where theantireflector is attached to the surface of the solar battery panel, thetransmittance of light increases. Therefore, the power generationefficiency of the solar battery improves.

(Retardation Plate)

The retardation plate of the invention includes the above-describedcorrugated pattern forming sheet 10. However, the direction ofirregularities is one direction rather than a random direction.

Even in the retardation plate of the invention, similarly to the aboveantireflector, one surface or both surfaces of the corrugated patternforming sheet 10 may be provided with other layers. For example, astain-proof layer may be provided on the surface of the corrugatedpattern forming sheet 10 on the side where the corrugated pattern 12 ais formed.

Also, on the surface of the corrugated pattern forming sheet 10 on theside where the corrugated pattern 12 a is not formed, the surface may beprovided with, for example, a base material. Examples of the basematerial include a sheet made of resin such as triacetylcellulose.

Moreover, the surface opposite to the surface where the corrugatedpattern is formed may be further provided with a corrugated pattern.

In the retardation plate of the invention, the effect of developing aretardation can be exhibited markedly. This is because, as describedabove, the average pitch A of the corrugated pattern 12 a of thecorrugated pattern forming sheet 10 is as short as 1 μm or less, and theaverage depth B is as large as 10% or more when the average pitch A is100%, and therefore a portion where air and the corrugated patternforming sheet 10 whose refractive indexes are different from each otherare alternately arranged becomes long in the thickness direction, sothat a portion showing optical anisotropy becomes long. Moreover, in acase where the pitch of a corrugated pattern is approximately equal toor less than the wavelength of visible light, the same retardation canbe caused over a broad visible light wavelength range.

(Original Process Sheet Plate)

The original process sheet plate includes the above-described corrugatedpattern forming sheet 10, and is used as a die for allowing a corrugatedpattern to be transferred to other raw materials using methods as shownbelow, thereby manufacturing a corrugated pattern forming sheet, whichhas a corrugated pattern with the same average pitch and average depthas the original process sheet plate and which can be used as an opticalelement, such as an antireflector or a retardation plate, on a largescale with large area.

The original process sheet plate may be provided with a support made ofresin or metal for supporting the corrugated pattern forming sheet 10.

The specific method for manufacturing an optical element using theoriginal process sheet plate may include, for example, the followingmethods (a) to (c).

(a) A method for coating an uncured ionizing radiation-curable resin onthe surface of an original process sheet plate in which a corrugatedpattern is formed, irradiating the curable resin with ionizing radiationto cure the curable resin, and then peeling off the cured coated filmfrom the original process sheet plate. Here, although the ionizingradiation is typically ultraviolet rays or electron rays, the inventionalso includes visible rays, X rays, ionic rays, etc. as the ionizingradiation.

(b) A method for coating an uncured liquid thermosetting resin on thesurface of an original process sheet plate in which a corrugated patternis formed, heating and curing the liquid thermosetting resin, and thenpeeling off the cured coated film from the original process sheet plate.

(c) A method for bringing a sheet-like thermoplastic resin into contactwith the surface of an original process sheet plate in which acorrugated pattern is formed, heating and softening thermoplastic resinwhile being pressed against the original process sheet plate, coolingthermoplastic resin, and then peeling off the cooled sheet-likethermoplastic sheet from the original process sheet plate.

It is possible to prepare a secondary process sheet by using theoriginal process sheet plate and to manufacture an optical element byusing the secondary process sheet. Specific methods using a secondaryprocess sheet include the following methods (d) to (f).

(d) A method of laminating a metal plating layer (material fortransferring corrugated pattern) by plating a metal, such as nickel, onthe surface of an original process sheet plate in which a corrugatedpattern is formed, peeling off the metal plating layer from the originalprocess sheet plate to prepare a secondary process sheet made of metal,then coating an uncured ionizing radiation-curable resin on the surfaceof the secondary process sheet which has been in contact with thecorrugated pattern, irradiating the curable resin with ionizingradiation to cure the curable resin, and then peeling off the curedcoated film from the secondary process sheet.

(e) A method of laminating a metal plating layer (material fortransferring corrugated pattern) on the surface of an original processsheet plate in which a corrugated pattern is formed, peeling off themetal plating layer from the original process sheet plate to prepare asecondary process sheet made of metal, coating an uncured liquidthermosetting resin on the surface of the secondary process sheet whichhas been in contact with the corrugated pattern, curing the resin byheating, and then peeling off the cured coated film from the secondaryprocess sheet.

(f) A method of laminating a metal plating layer (material fortransferring corrugated pattern) on the surface of an original processsheet plate in which a corrugated pattern is formed, peeling off themetal plating layer from the original process sheet plate to prepare asecondary process sheet made of metal, bringing a sheet-likethermoplastic resin into contact with the surface of the secondaryprocess sheet which has been in contact with a corrugated pattern,heating and softening thermoplastic resin while being pressed againstthe secondary process sheet, cooling thermoplastic resin, and thenpeeling off the cooled sheet-like thermoplastic sheet from the secondaryprocess sheet.

A specific example of the method (a) will be described. As shown in FIG.7, first, an uncured liquid ionizing radiation-curable resin 112 c iscoated on the surface of a web-like original process sheet plate 110where a corrugated pattern 112 a is formed by a coater 120. Next, theoriginal process sheet plate 110 on which the curable resin is coated ispressed by allowing a roll 130 to pass on the sheet, whereby the insideof the corrugated pattern 112 a of the original process sheet plate 110is filled with the curable resin. Thereafter, the curable resin isbridged and cured by irradiating the curable resin with ionizingradiation by an ionizing radiation irradiating apparatus 140. Then, aweb-like optical element 150 can be manufactured by peeling off thecured ionizing radiation-curable resin from the original process sheetplate 110.

In the method (a), a layer made of silicone resin, fluororesin, etc. andhaving a thickness of about 1 to 10 nm may be provided on the surface ofan original process sheet plate in which a corrugated pattern is formed,for the purpose of giving releasability before coating of an uncuredionizing radiation-curable resin.

The coater for coating an uncured ionizing radiation-curable resin onthe surface of an original process sheet plate in which a corrugatedpattern is formed, may include a T-die coater, a roll coater, a barcoater, etc.

The uncured ionizing radiation-curable resin may include a resincontaining one or more kinds of components selected from prepolymers,such as epoxy acrylate, epoxidized oil acrylate, urethane acrylate,unsaturated polyester, polyester acrylate, polyether acrylate,vinyl/acrylate, polyene/acrylate, silicon acrylate, polybutadiene, andpolystyrylmethylmethacrylate; and monomers, such as aliphatic acrylate,alicyclic acrylate, aromatic acrylate, hydroxyl-containing acrylate,allyl-containing acrylate, glycidyl-containing acrylate,carboxyl-containing acrylate, and halogen-containing acrylate. Theuncured ionizing radiation-curable resin is preferably diluted with asolvent, etc.

Further, fluororesin, silicone resin, etc. may be added to the uncuredionizing radiation-curable resin.

In a case where the uncured ionizing radiation-curable resin is curedwith ultraviolet rays, it is preferable to add photopolymerizationinitiators, such as acetophenones and benzophenones, to the uncuredionizing radiation-curable resin.

After the uncured liquid ionizing radiation-curable resin is coated, thecurable resin may be irradiated with ionizing radiation after a basemade of resin, glass, etc. is pasted thereto. Ionizing radiation may beemitted from either a base or an original process sheet plate havingionizing radiation transmittability.

The thickness of the sheet of ionizing radiation-curable resin aftercuring is preferably set to about 0.1 to 100 μm. If the thickness of thesheet of ionizing radiation-curable resin after curing is 0.1 μm ormore, sufficient strength can be secured, and if the thickness is 100 μmor less, sufficient flexibility can be secured.

In the above method shown in FIG. 7, the original process sheet plate isa web-like sheet, but it may be a leaf-like sheet. In a case where theleaf-like sheet is used, a stamping method for using the leaf-like sheetas a flat plate-like die, a roll-in printing method for winding theleaf-like sheet around a roll to use it as a cylindrical die, etc. canbe applied. Further, a leaf-like original process sheet plate may bearranged inside a die of an injection molding machine.

However, in the method for using these leaf-like sheets, it is necessaryto repeat a process of forming a corrugated pattern multiple times inorder to produce optical elements on a large scale. In a case where thereleasability between an ionizing radiation-curable resin and anoriginal process sheet plate is low, clogging occurs in a corrugatedpattern when the process is repeated multiple times, and transfer of thecorrugated pattern tends to become imperfect.

On the other hand, in the method shown in FIG. 7, a corrugated patterncan be continuously formed with large area because the original processsheet plate is a web-like sheet. Therefore, even if the number of timesof repeated use of a corrugated pattern forming sheet is few, a requiredquantity of optical elements can be manufactured in a short time.

In the method (e) and (b), the liquid thermosetting resin may include,for example, uncured melamine resin, urethane resin, epoxy resin, etc.

Further, the curing temperature in the method (b) is preferably lowerthan the glass transition temperature of an original process sheetplate. This is because there is a possibility that a corrugated patternof the original process sheet plate may deform during curing if thecuring temperature is higher than the glass transition temperature ofthe original process sheet plate.

In the method (c) and (f), thermoplastic resin may include, for example,acrylic resin, polyolefin, polyester, etc.

A pressure when pressing the sheet-like thermoplastic resin against thesecondary process sheet is preferably from 1 to 100 MPa. When thepressure is 1 MPa or more, it is possible to transfer a corrugatedpattern with high accuracy, and when the pressure is 100 MPa or less, itpossible to prevent excess pressure from being applied.

Further, the heating temperature of thermoplastic resin in the method(c) is preferably lower than the glass transition temperature of anoriginal process sheet plate. This is because there is a possibilitythat a corrugated pattern of the original process sheet plate may deformduring heating if the heating temperature is higher than the glasstransition temperature of the original process sheet plate.

A cooling temperature after heating is preferably less than the glasstransition temperature of the thermoplastic resin so as to be able totransfer a corrugated pattern with high accuracy.

Among the methods (a) to (c), the method (a) of using an ionizingradiation-curable resin in that heating can be omitted and deformationof a corrugated pattern of an original process sheet plate can beprevented is preferable.

In the methods (d) to (f), the thickness of a secondary process sheetmade of metal is preferably set to about 50 to 500 μm. If the thicknessof the secondary process sheet made of metal is 50 μm or more, thesecondary process sheet has sufficient strength, and if the thickness is500 μm or less, sufficient flexibility can be secured.

In the methods (d) to (f), a metal sheet with small thermal deformationis used as a process sheet. Therefore, any of an ionizingradiation-curable resin, a thermosetting resin, and a thermoplasticresin can be used as a material for corrugated pattern forming sheets.

In the methods (d) to (f), the secondary process sheet is obtained bytransferring the corrugated pattern of the original process sheet plateto a metal; however the secondary process sheet may be obtained bytransferring to resin. In this case, the resin which can be usedincludes, for example, polycarbonate, polyacetal, polysulfone, andionizing radiation-curable resin used in the method (a). When using anionizing radiation-curable resin, the ionizing radiation-curable resinis performed in order of coating, curing, and peeling, similar to themethod (a).

An adhesive layer may be provided in the surface of an optical elementobtained as described above, which is opposite to the surface in which acorrugated pattern is formed. Moreover, a further corrugated pattern maybe formed in the surface opposite to the surface where the corrugatedpattern is formed.

Further, the corrugated pattern forming sheet or secondary process sheetused as an original process sheet plate may be used as a protectivelayer without peeling off, and the protective layer may be peeled offimmediately before use of an optical element.

EXAMPLES

The present invention will now be described in more detail by way ofexamples, but the present invention is not limited to the followingexamples. In the following examples, parts and percentages are by weightunless otherwise specified.

The Young's moduli in the following examples are values which aremeasured by using a tensile testing machine (Tensiron RTC-1210 made byOrientec Corp.), setting temperature to 23° C., according to the “Methodfor testing the Young's modulus of a metallic material at an elevatedtemperature” of JIS Z 2280-1993. This is the same even in a case wherethe hard layer is made of a metallic compound.

Manufacture Example 1

A laminated sheet was obtained by vacuum-depositing titanium having aYoung's modulus of 115 GPa on one surface of a polyethyleneterephthalate shrink film (Hishipet LX-10S made by Mitsubishi Plastics,Inc.) that thermally shrinks uniaxially, has a thickness of 50 μm, andhas a Young's modulus of 3 GPa so as to have a thickness of 3 nm,thereby forming a smooth surface hard layer.

Next, a corrugated pattern forming sheet whose hard layer has a wavelikecorrugated pattern which has a period in a direction orthogonal to ashrinking direction was obtained by heating the laminated sheet for 1minute at 100° C., and making the sheet thermally shrink to 40% of alength before heating (that is, making the sheet deformed at adeformation ratio of 60%).

Manufacture Example 2

A corrugated pattern forming sheet was obtained similarly to ManufactureExample 1 except for vacuum-depositing titanium so as to have athickness of 7 nm.

Manufacture Example 3

A corrugated pattern forming sheet was obtained similarly to ManufactureExample 1 except for heating the laminated sheet for 1 minute at 75° C.,and making the sheet thermally shrink to 70% of a length before heating(that is, making the sheet deformed at a deformation ratio of 30%).

Manufacture Example 4

A corrugated pattern forming sheet was obtained similarly to ManufactureExample 1 except that a polyethylene terephthalate shrink film (HishipetPX-40S made by Mitsubishi Plastics, Inc.) that thermally shrinksbiaxially, has a thickness of 50 μm, and has a Young's modulus of 3 GPawas used instead of Hishipet LX-10S. In the corrugated pattern formingsheet of Manufacture Example 4, the hard layer has a wavelike corrugatedpattern which does not run in a specific direction.

Manufacture Example 5

A corrugated pattern forming sheet was obtained similarly to ManufactureExample 1 except that platinum having a Young's modulus of 168 GPa wasvacuum-deposited so as to have a thickness of 3 nm instead of vacuumdeposition of titanium.

Manufacture Example 6

A corrugated pattern forming sheet was obtained similarly to ManufactureExample 1 except that silicon dioxide having a Young's modulus of 72 GPawas vacuum-deposited so as to have a thickness of 3 nm instead of vacuumdeposition of titanium.

Manufacture Example 7

A corrugated pattern forming sheet was obtained similarly to ManufactureExample 1 except that titanium dioxide having a Young's modulus of 300GPa was vacuum-deposited so as to have a thickness of 1 nm instead ofvacuum deposition of titanium. This corrugated pattern forming sheet hasa self-cleaning function which decomposes an organic matter adhering toa surface when it is irradiated with light.

Manufacture Example 8

A corrugated pattern forming sheet was obtained similarly to ManufactureExample 1 except that gallium arsenide having a Young's modulus of 83GPa was chemically deposited so as to have a thickness of 3 nm insteadof vacuum deposition of titanium.

Manufacture Example 9

A sheet made of polydimethyl siloxane having a Young's modulus of 2 MPaand having a thickness of 5 mm was pulled until it became twice as longas itself by a pulling device, and was fixed in that state. Then, inthat state, a laminated sheet was obtained by vacuum-depositing titaniumhaving a Young's modulus of 115 GPa on one surface of the sheet so as tohave a thickness of 3 nm, thereby forming a smooth surface hard layer.

Next, a corrugated pattern forming sheet whose hard layer has a wavelikecorrugated pattern which has a period in a direction orthogonal to acompression direction was obtained by stopping the pulling, and thenreturning the laminated sheet to its length before the pulling, therebycompressing the hard layer at a deformation ratio of 50%.

Manufacture Example 10

A laminated sheet in which a resin layer and a smooth surface hard layerwere laminated was obtained by vacuum-depositing titanium having aYoung's modulus of 115 GPa on one surface of a sheet made ofpolydimethyl siloxane having a Young's modulus of 2 MPa and having athickness of 5 mm so as to have a thickness of 3 nm.

Next, a corrugated pattern forming sheet whose hard layer has a wavelikecorrugated pattern which has a period in a pulling direction wasobtained by pulling the laminated sheet to five times as long as itselfby a pulling device, thereby making the sheet shrink to 50% in adirection orthogonal to the pulling direction (that is, making the sheetdeformed at a deformation ratio of 50%).

Manufacture Example 11

A corrugated pattern forming sheet was obtained similarly to ManufactureExample 1 except that titanium was vacuum-deposited so as to have athickness of 15 nm.

Manufacture Example 12

An attempt was made to obtain a corrugated pattern forming sheetsimilarly to Manufacture Example 1 except that a polyethyleneterephthalate film (G2 made by Teijin Ltd.) that stretches biaxially,has a thickness of 50 μm, and has a Young's modulus of 5 GPa was usedinstead of the shrink film. However, the corrugated pattern formingsheet was not obtained.

Manufacture Example 13

A laminated sheet was obtained by vacuum-depositing titanium having aYoung's modulus of 115 GPa on one surface of a polyethyleneterephthalate shrink film (Hishipet LX-10S made by Mitsubishi Plastics,Inc.) that thermally shrinks uniaxially, has a thickness of 50 μm, andhas a Young's modulus of 3 GPa so as to have a thickness of 3 nm,thereby forming a smooth surface hard layer.

Next, a corrugated pattern forming sheet was obtained similarly toManufacture Example 1 except that the laminated sheet was heated for 1minute at 70 C, and making the sheet thermally shrink to 97% of a lengthbefore heating (that is, making the sheet deformed at a deformationratio of 3%).

Manufacture Example 14

An optical element was obtained as follows, using the corrugated patternforming sheet obtained by Manufacture Example 1 as an original processsheet plate.

That is, an uncured ultraviolet-curable resin composition containing anepoxy acrylate-based prepolymer, 2-ethylhexyl acrylate, and abenzophenone-based photopolymerization initiator was coated on thesurface of the original process sheet plate obtained by ManufactureExample 1, in which a corrugated pattern was formed.

Next, a triacetyl cellulose film having a thickness of 50 μm wassuperposed on and pressed against the surface of the coated film of theuncured ultraviolet-curable resin composition which is not in contactwith the original process sheet plate.

Next, an optical element was obtained by irradiating the triacetylcellulose film with ultraviolet rays to cure the uncuredultraviolet-curable resin, and peeling off the laminated product of thecured substance and triacetylcellulose from the original process sheetplate.

Manufacture Example 15

An optical element was obtained as follows, using the corrugated patternforming sheet obtained by Manufacture Example 1 as an original processsheet plate.

That is, a nickel-plated sheet having a thickness of 200 μm was obtainedby performing nickel plating on the surface of the original processsheet plate obtained by Manufacture Example 1, in which a corrugatedpattern was formed, and peeling off the nickel plating. Then, an uncuredultraviolet-curable resin composition containing an epoxy acrylate-basedprepolymer, 2-ethylhexyl acrylate, and a benzophenone-basedphotopolymerization initiator was coated on the surface of thenickel-plated sheet which was contacted with the original process sheetplate.

Next, a triacetyl cellulose film having a thickness of 50 μm wassuperposed on and pressed against the surface of the coated film of theuncured ultraviolet-curable resin composition which is not in contactwith the nickel-plated sheet.

Next, an optical element was obtained by irradiating the triacetylcellulose film with ultraviolet rays to cure the uncured curable resin,and peeling off the laminated product of the cured substance andtriacetylcellulose from the nickel-plated sheet.

Manufacture Example 16

An optical element was obtained similarly to Manufacture Example 14except that a thermosetting epoxy resin was used instead of theultraviolet-curable resin composition, and thermosetting epoxy resin wascured by heating instead of radiating ultraviolet rays.

Manufacture Example 17

A nickel-plated sheet having a thickness of 200 μm was obtainedsimilarly to Manufacture Example 14. Then, a polyacrylamide film havinga thickness of 50 μm was superposed on the surface of the nickel-platedsheet which has contacted with the original process sheet plate, and thefilm was then heated. An optical element was obtained by pressing thepolyacrylamide film softened by heating and the nickel-plated sheet fromboth sides thereof, cooling and curing them, and then peeling off thecured polyacrylamide film from the nickel-plated sheet.

The top surfaces of the corrugated pattern forming sheets of ManufactureExamples 1 to 11, and 13 and the top surfaces of the optical elements ofManufacture Examples 14 to 17 were captured by an atomic forcemicroscope (Nanoscope III made by Veeco Instruments).

In the corrugated pattern forming sheets of Manufacture Examples 1 to 3,5 to 11, and 13 and the optical elements of Manufacture Examples 14 to17, the pitches of each corrugated pattern were measured at ten placesin an image captured by the atomic force microscope, and the measuredpitches were averaged, thereby obtaining an average pitch.

The average pitch of the corrugated pattern forming sheet of ManufactureExample 4 was obtained by the method for Fourier-transforming an imageof a corrugated pattern, which is described in above.

As for averages depths of the corrugated pattern forming sheets ofManufacture Examples 1 to 11, and 13 and the optical elements ofManufacture Examples 14 to 17, the depths of individual bottoms of eachcorrugated pattern were measured at ten places in a cross-sectionalimage obtained by the atomic force microscope, and the measured depthswere averaged, thereby obtaining an average depth.

These values are shown in Table 1.

Further, suitability as optical elements was evaluated according to thefollowing standards from the average pitches of the corrugated patternsand the average depths of the bottoms. The evaluation results are shownin Table 1.

O: The average pitch of a corrugated pattern is 1 μm or less, and theaverage depth is 10% or more given an average pitch of 100%;consequently, the sheet is suitable as an optical element.

X: The average pitch of a corrugated pattern is over 1 μm, and theaverage depth is less than 10% given an average pitch of 100%; thus thesheet is not suitable as an optical element.

TABLE 1 Depth of Pitch of Deepest Corrugated Portion of Depth/ PatternCorrugated Pitch Evalua- (nm) Pattern (nm) (%) tion Manufacture Example1 300 300 100 ◯ Manufacture Example 2 700 700 100 ◯ Manufacture Example3 300 90 30 ◯ Manufacture Example 4 300 250 83 ◯ Manufacture Example 5250 250 100 ◯ Manufacture Example 6 200 200 100 ◯ Manufacture Example 7250 250 100 ◯ Manufacture Example 8 220 220 100 ◯ Manufacture Example 9300 200 67 ◯ Manufacture Example 10 300 200 67 ◯ Manufacture Example 111100 700 64 X Manufacture Example 12 A corrugated pattern is not formedX Manufacture Example 13 300 28 9 X Manufacture Example 14 300 300 100 ◯Manufacture Example 15 300 300 100 ◯ Manufacture Example 16 300 300 100◯ Manufacture Example 17 300 300 100 ◯

In the manufacturing methods of Manufacture Examples 1 to 11, and 13 inwhich a laminated sheet in which a smooth surface hard layer made of ametal or a metallic compound was provided on one surface of a resinlayer was shrunken or compressed, corrugated pattern forming sheetscould be manufactured easily. Particularly in the corrugated patternforming sheets obtained in Manufacture Examples 1 to 10, the averagepitch of each corrugated pattern is 1 μm or less, and the average depthof the bottom is 10% or more given an average pitch of 100%.Consequently, the sheets were suitable as optical elements. The reasonthe average pitches and average depths as described above were obtainedin Manufacture Examples 1 to 10 is that the thickness of the smoothsurface hard layer was 10 nm or less, the Young's modulus was low, thedeformation ratio was set to 30% or more.

In addition, in Manufacture Example 11, the thickness of the smoothsurface hard layer was over 10 nm. Therefore, as for the obtainedcorrugated pattern forming sheet, the average pitch of the corrugatedpattern was over 1 μm. In addition, in Manufacture Example 13, thedeformation ratio was set to 3%. Therefore, as for the obtainedcorrugated pattern forming sheet, the average depth of the bottom of acorrugated pattern was less than 10% given an average pitch of 100%.These are not necessarily suitable as optical elements.

Further, according to the manufacturing methods of Manufacture Examples14 to 17 using the corrugated pattern forming sheet obtained inManufacture Example 1 as an original process sheet plate, opticalelements having a corrugated pattern of the same average pitch andaverage depth as the corrugated pattern forming sheet could bemanufactured simply and easily.

On the other hand, in Manufacture Example 12 using a biaxially stretchedpolyethylene terephthalate film as a resin layer, a smooth surface hardlayer was not meanderingly deformed. Therefore, a corrugated pattern wasnot formed.

The corrugated pattern forming sheet of the invention can be utilizedfor, for example, a polarizing plate, an abrasive film, a cell culturesheet, an electrolyte membrane for fuel cells, a die-releasing film, ananti-blocking film, an easy adhesion film, a film with improved printingperformance, etc. Further, the corrugated pattern forming sheet of theinvention can also be utilized for plural ones among the aboveapplications.

While preferred embodiments of the invention have been described andillustrated above, it should be understood that these are exemplary ofthe invention and are not to be considered as limiting. Additions,omissions, substitutions, and other modifications can be made withoutdeparting from the spirit or scope of the present invention.Accordingly, the invention is not to be considered as limited by theforegoing description but is only limited by the scope of the appendedclaims

1. A corrugated pattern forming sheet comprising a resin layer, and ahard layer provided at least in a portion of an outer surface of theresin layer, the hard layer having a wavelike corrugated pattern,wherein the hard layer is made of at least one metal or at least onemetallic compound, and wherein the average pitch of the corrugatedpattern is 1 μm or less, and the average depth of the bottom of thecorrugated pattern is 10% or more given an the average pitch of 100%. 2.The corrugated pattern forming sheet according to claim 1, wherein thehard layer is made of a metallic compound.
 3. The corrugated patternforming sheet according to claim 2, wherein the metallic compound isselected from the group consisting of titanium oxide, aluminum oxide,zinc oxide, magnesium oxide, tin oxide, copper oxide, indium oxide,cadmium oxide, lead oxide, silicon oxide, barium fluoride, calciumfluoride, magnesium fluoride, zinc sulfide, and gallium arsenide.
 4. Thecorrugated pattern forming sheet according to claim 1, wherein the hardlayer is made of a metal.
 5. The corrugated pattern forming sheetaccording to claim 4, wherein the metal is at least one kind of metalselected from the group consisting of gold, aluminum, silver, carbon,copper, germanium, indium, magnesium, niobium, palladium, lead,platinum, silicon, tin, titanium, vanadium, zinc, and bismuth.
 6. Anantireflector comprising the corrugated pattern forming sheet of any oneof claims 1 to
 5. 7. A retardation plate comprising the corrugatedpattern forming sheet of any one of claims 1 to
 5. 8. An originalprocess sheet plate, comprising the corrugated pattern forming sheet ofany one of claims 1 to
 5. 9. A method for manufacturing an opticalelement comprising: coating an uncured curable resin onto a surface ofthe original process sheet plate of claim 8, and peeling a cured coatingfilm from the original process sheet plate after curing the curableresin.
 10. A method for manufacturing an optical element comprising:Contacting a sheet-like thermoplastic resin with a surface of theoriginal process sheet plate of claim 8; cooling the thermoplastic resinafter softening by heating while pressing to the original process sheetplate; and peeling the cooled sheet-like thermoplastic resin from theoriginal process sheet plate.
 11. A method for manufacturing an opticalelement comprising: laminating a material for transferring a corrugatedpattern onto a surface of the original process sheet plate of claim 8;preparing a secondary process sheet by peeling the material fortransferring the corrugated pattern laminated on the corrugated patternfrom the original process sheet plate; coating an uncured curable resinonto a surface of the secondary process sheet contacting the corrugatedpattern of the original process sheet plate; and peeling a cured coatingfilm from the secondary process sheet after curing the curable resin.12. A method for manufacturing an optical element comprising: laminatinga material for transferring a corrugated pattern onto a surface of theoriginal process sheet plate of claim 8; preparing a secondary processsheet is prepared by peeling the material for transferring thecorrugated pattern laminated on the corrugated pattern from the originalprocess sheet plate; contacting a sheet-like thermoplastic resin with asurface of the secondary process sheet contacting the corrugated patternof the original process sheet plate; cooling the thermoplastic resinafter softening by heating while pressing to the secondary processsheet; and peeling the cooled sheet-like thermoplastic resin from thesecondary process sheet.
 13. A method for manufacturing a sheet having acorrugated pattern, comprising using a sheet according to any one ofclaims 1-5 as a die to create a sheet with the same average pitch andaverage depth as the corrugated pattern forming sheet.